Abstract
| - Studies are reported on the assembly of the branched C-trisaccharide, α-d-Man-(1→3)-[α-d-Man-(1→6)]-d-Man, representing the core region of the asparagine-linked oligosaccharides. The key stepin this synthesis uses a SmI2-mediated coupling of two mannosylpyridyl sulfones to a C3,C6-diformylbranched monosaccharide unit, thereby assembling all three sugar units in one reaction and withcomplete stereocontrol at the two anomeric carbon centers. Subsequent tin hydride-based deoxygenation followed by a deprotection step produces the target C-trimer. In contrast to many of theother C-glycosylation methods, this approach employes intact carbohydrate units as C-glycosyldonors and acceptors, which in many instances parallels the well-studied O-glycosylation reactions.The synthesis of the C-disaccharides α-d-Man-(1→3)-d-Man and α-d-Man-(1→6)-d-Man is alsodescribed, they being necessary for the following conformational studies of all three carbohydrateanalogues both in solution and bound to several mannose-binding proteins.
|